Online research in philosophy

Over the last three decades, truth-condition theories have earned a central place in the study of linguistic meaning. But their honored position faces a threat from recent deflationism or minimalism about truth. It is thought that the appeal to truth-conditions in a theory of meaning is incompatible with deflationism about truth, and so the growing popularity of deflationism threatens truth-condition theories of meaning.

I present an account of truth values for classical logic, intuitionistic logic, and the modal logic s5, in which truth values are not a fundamental category from which the logic is defined, but rather, an idealisation of more fundamental logical features in the proof theory for each system. The result is not a new set of semantic structures, but a new understanding of how the existing semantic structures may be understood in terms of a more fundamental notion of logical consequence.

Propositional logic, also known as sentential logic and statement logic, is the branch of logic that studies ways of joining and/or modifying entire propositions, statements or sentences to form more complicated propositions, statements or sentences, as well as the logical relationships and properties that are derived from these methods of combining or altering statements. In propositional logic, the simplest statements are considered as indivisible units, and hence, propositional logic does not study those logical properties and relations that depend upon parts of statements that are not themselves statements on their own, such as the subject and predicate of a statement. The most thoroughly researched branch of propositional logic is classical truth-functional propositional logic, which studies logical operators and connectives that are used to produce complex statements whose truth-value depends entirely on the truth-values of the simpler statements making them up, and in which it is assumed that every statement is either true or false and not both. However, there are other forms of propositional logic in which other truth-values are considered, or in which there is consideration of connectives that are used to produce statements whose truth-values depend not simply on the truth-values of the parts, but additional things such as their necessity, possibility or relatedness to one another.

It is usually held that what distinguishes a good inference from a bad one is that a good inference is truth-preserving. Against this view, this paper argues that a logical inference is good or bad depending not on whether it is truth-preserving or not, but whether it belongs to a logical system the addition of which makes a deductively conservative extension of the derivation relations among the atomic statements. To so argue, the paper first contends that the meaning of the logical operators of classical logic is determined not by their connections to truth, but by their inferential roles. It is claimed in conclusion that there is no genuine issue over which logic, classical or intuitionistic, is the correct logic, for they are both conservative in the relevant sense.

Despite my concerted efforts to formulate the linguistic doctrine of (first-order) logical truth, explicitly not as a claim that stipulations governing logical particles suffice to generate the logical truths (LD(I)), but as a determination thesis (LD(III))--that stipulations that certain particles behave as the classical logical particles suffice to determine uniquely the class of logically valid sentences, whose emptiness is clear and relatively unproblematic--, Quine2 nevertheless managed to read me as having claimed “that the logical truths can be generated (sic!) by stipulations--hence conventions--without the regress”! This was all the more disheartening as Quine had also written, in earlier correspondence,3 concerning my answer to the regress argument of Quine’s “Truth by Convention”: “I think it a good answer.” That answer turned on the point that neither the conventionalist nor anyone else need justify the logical truths--as empty, they require no justification--but rather that logical rules are needed, and perfectly in order, to justify of any logical truth that indeed it requires no justification in virtue of membership in the privileged class. Evidently, Quine must have changed his mind about this, for he disparages my notion of a “stipulated universal trait”, such as ‘being red or not red’, by rhetorically asking: “But how, without prior logic, do we then infer, in particular, that the Taj Mahal has the trait?” (P. 206.) We agree that inferences cannot be made without logic, but why..

Truth, etc. is a wide-ranging study of ancient logic based upon the John Locke lectures given by the eminent philosopher Jonathan Barnes in Oxford. The book presupposes no knowledge of logic and no skill in ancient languages: all ancient texts are cited in English translation; and logical symbols and logical jargon are avoided so far as possible. Anyone interested in ancient philosophy, or in logic and its history, will find much to learn and enjoy here.

v. 1. Truth of the world -- v. 2 Truth of God -- v. 3. The spirit of truth.

Postmodernists claim that there is no truth. However, the statement 'there is no truth' is self-contradictory. This essay shows the following: One cannot state the idea 'there is no truth' universally without creating a paradox. In contrast, the statement 'there is truth' does not produce such a paradox. Therefore, it is more logical that truth exists.

The study of truth is often seen as running on two separate paths: the nature path and the logic path. The former concerns metaphysical questions about the ‘nature’, if any, of truth. The latter concerns itself largely with logic, particularly logical issues arising from the truth-theoretic paradoxes.

A formula is a contingent logical truth when it is true in every model M but, for some model M , false at some world of M . We argue that there are such truths, given the logic of actuality. Our argument turns on defending Tarski’s definition of truth and logical truth, extended so as to apply to modal languages with an actuality operator. We argue that this extension is the philosophically proper account of validity. We counter recent arguments to the contrary presented in Hanson’s ‘Actuality, Necessity, and Logical Truth’ (Philos Stud 130:437–459, 2006 ).